The Cryptographic Approach to the Problem of Protein Synthesis 



69 



of "punctuation". Indeed, a sequence of bases can be broken into a set of 

 non-oveiiapping triplets in three different ways depending upon the base with 

 which we start. The three dilTerent readings of tiie same template can be des- 

 cribed mathematically as 3n, 3n/l, and 3n/2 (3n/3 being the same as 3n). 



A| 



3.6 A 



As was suggested by Dr Barbara Law, three possible readings of the same 

 RNA template may explain an interesting regularity first noticed by Dr 

 Martynas Yeas. He observed about two years ago that, in a case of seven 

 proteins for which the sequences of amino acids were known, the total number 

 of amino acids in the protein molecule was a multiple of three : nine amino 

 acids in oxytocine and vasopressin, twenty-one in insulin A, thirty in insulin B, 

 thirty-nine in ACTH, 126 in ribonuclease, etc. This could be explained if one 

 assumes that each RNA template synthesizes the proteins in all three possible 

 vv'ays, and that these three different readings are afterwards united in one 

 linear sequence. If this were true, there must exist a cryptographic correlation 

 between the first, second, and third "thirds" of each protein molecule. One 

 thinks of how such a correlation could be checked, but it seems to be very 

 difficult indeed. Recently, though, the existence of such a correlation became 

 rather doubtful, since two protein sequences published recently contain 29 and 

 124 amino acids. 



In summing up, we should say that the problem of finding the nature of the 

 correlation between polynucleotide chains of nucleic acids, and the polypeptide 

 chains of the proteins is still unsolved, although various methods for establishing 

 such a correlation have been worked out. We may hope, however, that with 

 the increased number of known protein sequences, this problem will be solved 

 in one way or another. 



REFERENCES 



1. J. D. Watson and F. H. C. Crick: Molecular structure of nucleic acids. Nature, Lond. 



171, 737-738 (1953). 



2. E. Chargaff: for reference see S. Zamenhof, G. Brawerman, and E. Chargaff: On the 



deoxypentose nucleic acids from several micro-organisms. Biochim. Biophys. Acta. 9, 

 402-405 (1952). 



3. G. R. Wyatt: Nucleic acids of some insect viruses. /. C^'//. P/(V.v/o/. 36, 201-205 (1952). 



4. J. D. Watson and F. H. C. Crick: Genetical implications of the structure of deoxyri- 

 bose nucleic acid. Nature, Lond. 171, 964-967 (1953). 



6 



